Sketchpad
Original author(s)Ivan Sutherland
Initial release1963
PlatformLincoln TX-2
Typeanimation, drawing, drafting, CAD

Sketchpad (a.k.a. Robot Draftsman[1]) is a computer program written by Ivan Sutherland in 1963 in the course of his PhD thesis, for which he received the Turing Award in 1988, and the Kyoto Prize in 2012. It pioneered human–computer interaction (HCI),[2] and is considered the ancestor of modern computer-aided design (CAD) programs as well as a major breakthrough in the development of computer graphics in general. For example, the graphical user interface (GUI) was derived from Sketchpad as well as modern object-oriented programming. Using the program, Ivan Sutherland showed that computer graphics could be used for both artistic and technical purposes in addition to demonstrating a novel method of human–computer interaction.

History

Sutherland was inspired by the Memex from "As We May Think" by Vannevar Bush. Sketchpad inspired Douglas Engelbart to design and develop oN-Line System at the Augmentation Research Center (ARC) at the Stanford Research Institute (SRI) during the 1960s.

See History of the graphical user interface for a more detailed discussion of GUI development.

Software

The geometric data or "N-component element" for a straight line is composed of addresses to two other N-component elements representing the end points of the line, which each contain an X and Y coordinate.[3]

Sketchpad was the earliest program ever to utilize a complete graphical user interface.[2]

The clever way the program organized its geometric data pioneered the use of "master" ("objects") and "occurrences" ("instances") in computing and pointed forward to object oriented programming. The main idea was to have master drawings which one could instantiate into many duplicates. If the user changed the master drawing, all the instances would change as well.

Geometric constraints was another major invention in Sketchpad, letting the user easily constrain geometric properties in the drawing—for instance, the length of a line or the angle between two lines could be fixed.

As a trade magazine said, clearly Sutherland "broke new ground in 3D computer modeling and visual simulation, the basis for computer graphics and CAD/CAM".[4] Very few programs can be called precedents for his achievements. Patrick J. Hanratty is sometimes called the "father of CAD/CAM"[5] and wrote PRONTO, a numerical control language at General Electric in 1957, and wrote CAD software while working for General Motors beginning in 1961. Sutherland wrote in his thesis that Bolt, Beranek and Newman had a "similar program"[3] and T-Square was developed by Peter Samson and one or more fellow MIT students in 1962, both for the PDP-1.[6]

The Computer History Museum holds program listings for Sketchpad.[7]

Hardware

Sketchpad ran on the Lincoln TX-2 (1958) computer at MIT, which had 64k of 36-bit words. The user drew on the screen with the recently invented light pen, which relayed information on its position by computing at what time the light from the scanning Cathode-ray tube screen is detected.

To configure the initial position of the light pen, the word "INK" was displayed on the screen, which, upon tapping, initialised the program with a white cross to continue keeping track of the pen's movement relative to its previous position.[3] Of the 36 bits available to store each display spot in the display file, 20 gave the coordinates of that spot for the display system and the remaining 16 gave the address of the n-component element responsible for adding that spot to display.

The TX-2 was an experimental machine and the hardware changed frequently (on Wednesdays, according to Sutherland[8]). By 1975, the light pen and the Cathode-ray tube with which it had been used had been removed.[9]

Publications

The Sketchpad program was part and parcel of Sutherland's Ph.D. thesis at MIT and peripherally related to the Computer-Aided Design project at that time. Sketchpad: A Man-Machine Graphical Communication System.

See also

References

  1. ↑ Armstrong, Helen (2016). Digital design theory : readings from the field. New York: Princeton Architectural Press. p. 9. ISBN 978-1-61689-308-8.
  2. 1 2 Sears, Andrew; Jacko, Julie A. (19 September 2007). The Human–Computer Interaction Handbook: Fundamentals, Evolving Technologies and Emerging Applications, Second Edition. CRC Press. p. 5. ISBN 978-1-4106-1586-2. Retrieved 1 March 2013.
  3. 1 2 3 Sutherland, Ivan Edward (January 1963). "Sketchpad: A man-machine graphical communication system (courtesy Computer Laboratory, University of Cambridge UCAM-CL-TR-574 September 2003)". Massachusetts Institute of Technology. Retrieved 2006-12-26.
  4. ↑ "The CAD/CAM Hall of Fame". American Machinist. Penton Media. November 1, 1998. Retrieved March 18, 2013.
  5. ↑ "Patrick Hanratty spotlight". The Regents of the University of California. October 18, 2012. Retrieved March 17, 2013.
  6. ↑ Computer History Museum (15 May 2006). "The Mouse that Roared: PDP-1 Celebration Event (Running Time: 01:53:46)". Retrieved 2013-03-14.
  7. ↑ Ivan E. Sutherland (1963). "Sketchpad listings". Retrieved 2021-10-30.
  8. ↑ Sutherland, Ivan (2012). "The TX-2 Computer and Sketchpad" (PDF). Lincoln Laboratory Journal. 19 (1): 82–84. Retrieved 6 November 2022.
  9. ↑ Youngman, James. "Sequence Changes". TX-2 Project. Retrieved 6 November 2022.

Bibliography

External videos
video icon Sketchpad demo: Part 1 Part 2, YouTube
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